Electrical and Structural Characterization of Polyaniline Synthesized in Acid Medium Having Nickel Salts as Impurities

Abstract

Electrical properties of polyaniline (PANI) synthesized in a solution containing nickel salts are investigated. The structural characterization by scanning electron microscopy shows that PANI yielded in nickel chloride (NiCl2) has thicker structures with high porosity that increases insofar NiCl2 concentration does. The pH variation monitoring due to the nickel salt inclusion in solution shows that mass and thickness are strongly dependent on pH variation. Thermogravimetric investigation reveals that PANI formed in the presence of nickel salts is thermally more stable. This fact is more accentuated in samples produced in nickel nitrate and, also, produces the absorbance peak shift of some functional groups, as well as their intensification, as pointed by the infrared spectroscopy analysis. On the other side, the electrical characterization through the current–potential analysis shows that PANI conductivity is larger in PANI yielded in the presence of sulfates and lower in nitrates, while the impedance electrochemical analysis evidences the formation of a surface passivated PANI region having higher resistance and lower capacitance than PANI in bulk. Concerning the resistance of this region, the difference between surface and bulk PANI is smaller in the sample yielded in NiCl2, but the difference in capacitance is greater.